Cathode ray tube system with strip chart recorder display format

ABSTRACT

A time variant measured variable is graphically displayed in moving strip chart format on a cathode ray tube. During a scan line the electron beam is intensity modulated at a position on the scan line which represents the magnitude of the measured variable at a given time. The intensity of the electron beam at positions in successive scan lines is similarly intensity modulated to produce a trend line representing the magnitude of the variable along the strip chart format. During the scanning of a subsequent raster frame, a new data value of the measured variable is displayed at a selected position at an edge of the viewing area of the strip chart format in the location previously occupied by the next sequential value and the older data values are simultaneously displaced. The oldest data value is deleted from the format. During a raster scan the electron beam is modulated at different intensity levels to produce chart lines and time lines on the strip chart format. During each scan line the electron beam may be turned on between a reference position and the position at which the measured variable is recorded to produce a shaded trend line more readily distinguished from other trend lines on the face of the tube. In a modification, a color picture tube produces the different intensity traces so that chart lines, time lines and trend lines are all readily distinguishable one from the other.

United States Patent Foley et ai.

CATHODE RAY TUBE SYSTEM WITH STRIP CHART RECORDER DISPLAY FORMATInventors: Gerard M. Foley, Ambler; Gerard Mosley, Melrose Park, both ofPa.

[21] Appl. No.: 187,300

[ Aug. 14, 1973 played in moving strip chart format on a cathode raytube. During a scan line the electron beam is intensity modulated at aposition on the scan line which represents the magnitude of the measuredvariable at a given time. The intensity of the electron beam atpositions in successive scan lines is similarly intensity modulated toproduce a trend line representing the magnitude of the variable alongthe strip chart format. During the scanning of a subsequent rasterframe, a new data value of the measured variable is displayed at aselected position at an edge of the viewing area of the strip chartformat in the location previously occupied by the next se- [52] US. Cl.l78/6.8, 324/121 R, 340/324 R quemial value and the older dam values areSimumb [51] Int. Cl. H04n 7/18 neously displaced. The oldest data valueIS deleted [58] Field of Search 340/324 A;

324/121 R. 315/22 18 178/6 8 from the format. During a raster scan theelectron beam is modulated at different intensity levels to pro- 56]References Cited duce chart lines and time lines on the strip chartformat. During each scan line the electron beam may be UNITED STATESPATENTS turned on between a reference position and the posi- 3,406,38710/1968 Werme 340/324 A tion at which the measured variable is recordedto pro- 3,577,031 5/1971 Welsh A 315/22 duce a shaded trend line morereadily distinguished 3'474438 10/1969 Lauherm' 324/121 R from othertrend lines on the face of the tube. In a mod- :iasseu 2 7 ification, acolor picture tube produces the different inuger tensity traces so thatchart lines, time lines and trend h th Primary Examiner Howard w Bmtonlines are all readily distinguishable one from t e 0 er Attorney-RichardE. Kurtz et al.

[57] ABSTRACT A time variant measured variable is graphically dis- 17Claims, 23 Drawing Figures CRYSTAL 52 CLOCK CHART LINE, SYNCHRONIZING 5AND CONTROL COUNTERS GATING AND DECODING FOR CHART AND SYSTEM TIMING (A1 *x 37 ,/36 DASH H I TAL SYNCH VERTICAL IO'S/ZO'S CHART LINES B SYNC"100's CHAA T INNE O S 5; VIDEO B COMPOSITE ME g cousmea VIDEO C L'NESBLANK s1 45 42 SHADING CONTROL BLANKINC SYSTEM CONTROL TIMING SYSTEMSYSTEM CLOCK CONTROL DATA COUNTER DATA ME LINE DATA COUNTER CLOCK I TARRI TN 5 41 T E 1 E55 00mm I I GATES, DATA COUNTERS I I AND DECODERS A lsum l 39 REGISTER I g PARALLEL OUTPUTS CLOCK DATA LOAD CONTROL 1 RIALSHIFT REGISTER AND GATES SERML OUTPUT I INPU DECODED UPDATE a j T FASTREPLACE I DATA I SHIFT 1 CONTROL T SAMPLED DATA VALVES smFTARELAcE DATAI OUT CIRCULATE DATA DELAY LINE CLOCK Patented Aug. 14, 1973 3,752,917

13 Sheets-Sheet 1 Patented Aug. 14, 1973 3,752,917

15 Sheets-Sheet 2 CRYSTAL s2 CLOCK FIG. 2

L CHART LINE, SYNCHRONIZING 33 AND CONTROL COUNTERS I u I GATING ANDDECODING FOR CHART AND SYSTEM TIMING TELEVISIO 35 50k MONITOR 37 36 HORIITAL DASH SYNC VERTICAL 1o's/2o's CHART LINES B SYNC" 38 A cHATT LINES100's CHART LINES VIDEO COMPOSITE L'NES BLANK 45 L SHADING CONTROLBLANKING SYSTEM coATRo TIMIN L G SYSTEM SYSTEM CLOCK CONTROL DATA A ICOUNTER DATA TIME LINE DATA COUNTER CLOCK START wa TSNESS CONTROL V 41\GATES, DATA COUNTERS I AND DECODERS I I SHIFT I L REGISTER T PARALLEL{OUTPUTS CLOCK I 0ATA LOAD CONTROL SEMI SHIFT REGISTER AND GATES I5ER|AL ou uT- o PAT A PARALLEL INPUTS 2 2 E B I n DATA I SHIFT I QCONTROL:

SAMPLED DATA VALVES OUT CIRCULATE DATA SHIFT LRELACE DATA f;

DELAY LINE CLOCK Patented Aug. 14, 1973 3,752,917

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, 23 M no: 2% 5+ wPT CATHODE RAY TUBE SYSTEM WITH STRIP CHART RECORDERDISPLAY FORMAT BACKGROUND OF THE INVENTION This invention relates tomethods and apparatus for data display and more particularly to thedisplay of a measured variable in a moving strip chart format on acathode ray tube.

Moving pen strip chart type recorders have been extensively used inindustry to produce representations of measured dependent variables as afunction of an independent variable, usually time. For example, inelectric power generating plants moving pen recorders continuouslymonitor many of the parameters of power generation. The strip chartrecords provide an excellent visual representation of the operation ofthe plant at any given time. It has become common to record two or moremeasured variables on the same strip chart to provide a convenient wayof directly comparing these measured variables one with the other tobetter determine their interrelationships. While the format of analogstrip chart recorders has become widely accepted as a useful displaymedium, the extensive use of strip chart recorders has attendantproblems.

Strip chart recorders produce a large amount of records and quite oftenit is only portions of these records produced in short time intervalswhich need to be studied. Further, it is only possible to record alimited number of measured variables on a single strip chart recordwithout confusion. Often, two or more measured variables which theoperator wishes to compare are not recorded on the same strip chart. Infact, if a large number, such as 100, measured variables are beingrecorded, the chances of two measured variables, which are desired forcomparison, appearing on one strip chart are small.

Another disadvantage of the extensive use of strip chart recorders iscaused by the necessary physical distance separating the recorders. Inorder to observe all of the measured variables, it is necessary for theoperator to move from one strip chart recorder to another.

Finally, of course, strip chart recorders have the disadvantage ofmoving mechanical elements, such as the recorder pen. The movement ofmechanical elements places an inherent limit on the speed of response,and accuracy of a moving pen strip chart recorder.

One example of a strip chart recorder is shown in U.S. Pat. No.3,389,397 Lex et al.

Recently, cathode ray tubes have been extensively used for graphicaldata display. These devices avoid the problems of moving mechanicalelements which are present in strip chart recorders. Refer for exampleto A Color-Television Graph Plotter for Digital Computers, Claude A.Wiatrowski, Computer Design, April 1970, pages l33-l36. This articledescribes the display of graphs in multiple colors on a cathode raytube. "Drum and Scope Unit Plots Plant Variables," John Werme, ControlEngineering, November 1964, Page 109, describes the display of a processvariable on an oscilloscope type display screen. While graphic displaysystems of the foregoing type are extensively used in many applications,they are not suitable for use as a replacement for strip chart recordersin the monitoring of measured variables of industrial processes. As onereason, they are not capable of displaying the measured variables in aformat to which operators have become accustomed and which format isparticularly convenient for the monitoring of these measured variables.

SUMMARY OF THE INVENTION In accordance with this invention a measureddependent variable is displayed in moving strip chart format on acathode ray tube. The relationship between one or more measuredvariables, and another variable, usually time, is displayed as anerasable record on cartesian coordinates.

In carrying out the invention the electron beam is intensity modulatedat positions in the scan lines of the raster frames which represent themagnitude of the measured variable. For some selected subsequent rasterframes the data values are displaced with respect to the scan lines. Atleast one new data value is added at one extreme of the display and atleast one data value at the other extreme is deleted. In this manner, adisplay is obtained of a trend line representing the measured dependentvariable as a function of the independent variable, in this instancetime. In this manner a moving display of the measured variable as afunction of time is presented in a format which closely resembles thatof a moving strip chart recorder.

In accordance with another important aspect of this invention, shadingis provided for one or more of the trend lines. In carrying this out,the electron beam is intensity modulated between a reference positionand the position representing the magnitude of the measured variable oneach scan line. In this manner, the screen is brightened between areference line and the trend line. This has several advantages. Whenmore than one trend line is displayed, the trend line with shading canbe more easily distinguished from other trend lines. Also, the shadingclarifies the time sequence of widely separated data values and theshading makes it easier to perform a visual interpolation on rapidlychanging data values. Finally, the shaded trend line gives a visualimpression of the value of the time integral of the measured variable.

In accordance with another aspect of this invention, scale lines andtime lines are displayed with different intensities than the trendlines. This makes the scale lines and time lines more readilydistinguishable from the trend lines.

In accordance with another aspect of this invention, the differentintensities of the trend lines, scale lines and time lines are displayedby different colors on the face of a color cathode ray tube.

The foregoing and other objects, features and advantages of theinvention will be better understood from the following more detaileddescription, appended claims and drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a display produced by thisinvention;

FIG. 2 is a block diagram of the system;

FIGS. 3A 3D are representations of oscillograms of waveforms depictingthe operation of the system;

FIG. 4 is a representation of the appearance of a display with threetrend lines;

FIG. 5 shows the source of clock pulses and the counter;

FIG. 6 shows logic circuitry for producing different levels of thebrightness signal;

FIG. 7 shows the shift register;

FIG. 8 shows the data counters;

FIG. 9A shows the update flip flop;

FIG. 9B shows the interlace gates;

FIG. 10 shows the shift register control circuit;

FIG. 11 shows the delay line shift flip-flop;

FIG. 12 shows the shading switches and the logic circuitry for obtainingthe shading signal;

FIG. 13 shows the line counter;

FIG. 14 shows logic for obtaining the blanking signal;

FIG. 15 shows logic circuitry for producing signals, clearing the shiftregister and transfer of data into the shift register;

FIG. 16 shows the circuitry for producing scan line timing pulses;

FIG. 17 shows gates for producing timing and strobe pulses;

FIG. 18 shows inverting gates for producing logical ones; and

FIG. 19 shows a tape recording system which may be used with theinvention.

DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION FIG. 1 illustrates adisplay produced on the screen of a cathode. ray tube television monitorby the system of this invention. FIG. 1 is a negative representation ofthe display which appearson the cathode ray tube screen. That is, a veryheavy mark on FIG. 1 represents a very bright mark on the televisionscreen, a moderately heavy mark represents a moderately bright mark onthe screen and so on. FIG. 1 shows the display of only a single measuredvariable although more than one variable can be displayed.

In FIG. 1 the left-hand vertical scale or chart line 11 represents thelowest value the variable is expected or permitted to have, and theright-hand vertical scale line 13 represents the highest value thevariable can have. Other vertical scale lines such as 10 arid 12 form alinear chart with which the data marks representing the values of themeasured variable can be compared.

Successive values of the variable are represented by the data marks suchas 14. These marks occur at horizontal positions in each scan line ofthe raster field. The position represents the magnitude of the measuredvariable at a particular time. For example, the data mark 14 depicts amagnitude between 18 and 19 scale units. The series of data marks formsa trend line.

The most recent value of the variable is represented by the uppermostdata mark 15 and the oldest value displayed is represented by the datamark 16 at the bottom.

The continuous horizontal lines such as 21 are time lines. Each of thetime lines appears in association with a particular data markrepresenting the value of the variable measured at the time representedby the time line. The brightness of the time lines is less than thebrightness of the data marks so that the latter will not be obscured.The vertical time scale represented by these time lines is a measure ofreal time at which the data values of the measured variable were taken.

In FIG. 1, horizontal shading lines such as 22 extend from the verticalleft-hand scale line 11 to each data mark. In this case, the verticalscale line 11 is the reference line. These horizontal lines 22 may beswitched on or off at the option of the viewer to provide shading(actually brightening) of the screen to the left of the trend line.

This shading has several important functions. When more than one trendline is displayed, the trend line with shading can be readilydistinguished from other trend lines. Where successive data values varyin magnitude greatly, as do the data marks 23, 24 and 25, the shadingmakes it very easy to distinguish whether a particular data markrepresents a time earlier or later than that represented by another datamark. In FIG. 1, the shading makes it clear that the data mark 24occurred at a later time than the data mark 25. Also, when the datamarks are rapidly changing as are those between the marks 26 and 25 theshading makes it easier to perform a visual interpolation of the trendline.

The system shown in the block diagram of FIG. 2 generates such adisplay. The system includes a cathode ray tube television monitor 30.This monitor is of a conventional type having an electron beampositioning circuit which scans the electron beam in a raster field ofscan lines. The monitor 30 also has an intensity modulating controlcircuit which is controlled by a composite video signal applied to theinput 31. This composite video signal is in the form of an amplitudemodulated voltage carrying vertical and horizontal synchronizing pulsesand a video signal. The system of this invention generates such acomposite video signal.

A source of clock pulses 32 divides each scan line of the electron beaminto equal time increments. A counter 33 receives clock pulses. Theseclock pulses are decoded by the gating and decoding circuitry 34 whichgenerates signals for intensifying the brightness of the cathode rayscreen at selected positions on each scan line. For example, the gatingcircuit 34 produces signals on the lines 35-37 at predetermined countintervals. These outputs (subsequently referred to as a second output)produce the scale lines, for example, the scale lines 10, 11 and 12 ofFIG. 1. The outputs on lines 35, 36 and 37 are combined into thecomposite video signal by the combiner 38.

The gating and decoding circuits 34 also produce horizontal sync andvertical sync pulses which are similarly combined into the compositevideo signal by the combiner 38. The gating and decoding circuit 34 alsoproduces a signal referred to as data dot dash. This signal modulatesthe intensity of data marks along a trend line. This technique is usefulwhen a plurality of trend lines are displayed in order to distinguishone trend line from another.

The sampled data values of the measured variableare supplied to thesystem of FIG. 2 in conventional binary coding at the terminals labeledsampled data values." In the system to be described each sampled datavalue is contained in a 10-bit word. A digital data storage devicestores a binary coded serial data stream of these data values. Thisdigital data storage device includes shift register 39 and acousticdelay line 40. The acoustic delay line 40 normally forms a circulatingpath for the data values.

In the system being described there are 465 visible scan lines in araster field. Therefore there are normally 465 data values for eachtrend line circulating in the digital data storage device. The system iscapable of displaying three trend lines. Therefore, there are threeten-bit word data values for each scan line. (Actually 31-bit words areused out of 35 available bit positions, 30 bits being used for the datavalues and 1 bit being used for the time line.)

The data words, or values, circulating to shift register 39 are decodedby circuitry indicated as gates, data counters and decoders 41. At aposition in each scan line, which position is denoted by the data word,a data brightness pulse is produced on the line 42. (The data brightnesspulse is subsequently referred to as a first output signal.) This outputsignal is also combined into the composite video signal by the combiner38.

The gates, data counters and decoders 41 also produce a time linecontrol signal on the output line 43. The time line control signal(subsequently referred to as a third output) is mixed into the compositevideo signal to modulate the intensity of the electron beam at adifferent intensity level to produce the time lines such as the lines 21in FIG. 1.

The data words recirculating in the delay line 40 and circulating toshift register 39 are decoded during a first raster frame to produce one(or more) trend lines. At the beginning of a subsequent raster frame, a31-bit data word representing a new data value is inserted in the streamcirculating in the delay line in the position formerly occupied by thedata word representing the next most recent value of the measuredvariable. The latter is inserted in the place formerly occupied by thenext older data word and so on. In this manner the data storage deviceis updated with each data word being displaced with respect to the scanline on which it was previously displayed. At least one new data valueis added at one extreme of the display and at least one data value isdeleted at the other extreme of the display. The updating function isindicated by the switch 44 in FIG. 2. Normally this switch is in thelower position so that the data words in the stream recirculate from theoutput to the input of the acoustic delay line 40. These data words arealso shifted into the shift register 39 for readout. During an updateoperation the switch 44 is actuated to its upper position. Data valuesthen recirculate from the output of the shift register to the input ofthe delay line. The new value is inserted at the appropriate place inthe bit stream. Now there are 466 data values in the bit stream.

The switch is restored to its lower position when the shift registercontains the data value which previously controlled the last raster lineof the display. This procedure results in 465 values, including one newvalue and lacking one old value, circulating in the delay line,automatically synchronized with the scanning so as to appear on thescreen in the same place as did the old data sequence. The lengtheningof the bit stream caused the data values to be shifted by one positionwith respect to the scan line on which they are displayed.

Summarizing the update, during a first raster field, each data word inthe stream modulates the electron beam during one scan linef'the firstword, representing the measured variable at a first time, modulates thefirst scan line; the second word modulates the second scan line and soon. During a subsequent raster field, a new data value. representing themeasured variable at a second time, (either earlier or later), modulatesthe first scan line. All subsequent scan lines are modulated by the datawords which have been shifted in position in the bit stream with respectto the scan lines.

During periodic updating the display on the monitor screen appears tomove downward as if a piece of paper bearing the markings on the screenwere being unrolled and written on at the top and rolled out of sight atthe bottom.

All the operations of the system are under control of the system controlindicated at 45. This control produces blanking pulses to blank theelectron beam during retrace. It also provides clock pulses and loadcontrol pulses to the shift register 39.

OPERATION OF THE SYSTEM The operation of the system will be apparentfrom FIGS. 3A-3D which are representations of oscillograms of thewaveforms of the composite video signal and the synchronizing signals.FIGS. 3A through 3C each show the composite video signal during thescanning of one scan line. FIG. 3A shows the pulses, such as 70, whichoccur at every 10 clock pulses. Pulses such as 71 occur at every 50clock pulses and pulses such as 72 occur at every 100 clock pulses. Theheight of the pulses -72 determines the relative intensity of the chartlines.

FIG. 3B shows the composite video signal with the same scan mark pulses,and in addition, it shows a pulse which produces one of the data markson each scan line. The pulse 73 produces a data mark on each scan linerepresenting a measuring value.

FIG. 3C shows the foregoing pulses and additionally shows the signalwhich produces shading between the reference mark pulse 79 and the datamark pulse 73. Note that the composite video signal has an amplitudewhich is the same as the amplitude of the pulse 70 during the portion ofthe scan line from zero (left-hand edge) to the data mark pulse 73. Thisintensities the beam to the same brightness as the tens chart marks.

FIG. 3D shows the vertical and horizontal sync signals. The time betweenthe points 74 and 75 is one complete frame. At 76 the vertical syncsignal occurs. This causes the electron beam to shift back from the endof the last scan line displayed to the beginning of the first scan linedisplayed on the next frame. The other regularly occurring pulses 77,78shown in FIG. 3D are the horizontal sync pulses which occur at the endof each scan line.

FIG. 4 is an artists representation of a display in which three measuredvariables are displayed as the trend lines 50,51 and 52. The display ofFIG. 4 has I00 chart lines but the specific system being described isalso capable of producing a 50-line display.

The chart lines such as 53,54, and 55 in FIG. 4 are produced at everyten time increments, that is, ten clock pulses. The lines 53,54 and 55and other similar lines are intensified to the lowest level ofbrightness. At every 50 time increments a line such as the line 56 isintensified to an intermediate level of brightness. At every timeincrements a scale line such as S7 is intensified to a high level ofbrightness. The data marks making up the trend lines 50-52 areintensified to a fourth, highest'le'vel of brightness. In FIG. 4 theshading indicated by reference numeral 58 is at the same intensity levelas the scale lines 53-55. The shading is represented in FIG. 4 bydiagonal and vertical cross hatching which is not present on the screenof an actual display.

DETAILED DESCRIPTION OF THE SYSTEM A detailed schematic of the system ofFIG. 2 is shown in FIGS. 5-18. These figures do not show in detail theconventional television monitor 30. In the specific embodiment beingdescribed it is a CONRAC Model CQF 17/ 1024/81 television monitor whichdisplays 60 frames per second. Each raster frame has a nominal 513 scanlines. Of these 513 lines, 465 lines are visible and 48 scan line timesare allowed for vertical flyback.

The acoustic delay line is a Tyco Digital Devices 3l9E-2-83magnetostrictive delay line having a delay of 8.333 milliseconds and abit rate of 2.1546X bits per second.

The remainder of the system is depicted in FIGS. 5-18 as executed withlogical elements in which logical zero is represented by ground level,and logical one is represented by a positive signal. The system includesintegrated circuit modules designated, for example, M102 or N707. Mostof these circuit modules contain two or more functional circuitelements. In general a particular functional circuit element isidentified by appending a number designating an output terminal of themodule. Thus, for example, the two of the four elements contained inmodule M102 (top left of FIG. 5) are designated Ml02-8 and M102-l1. Atable at the end of this section, identifies typical components suitablefor use. For example, gate M102-8 identifies one gate of a quad NORgate.

THE SOURCE OF CLOCK PULSES AND THE TIME INCREMENT COUNTER, FIG. 5

In FIG. 5 the source of clock pulses is the quartz crystal clock 32. Thepulses from this clock are applied to a counter including the .II(flip-flop stages Ml01-M302. As indicated these stages provide two divideby 5 counters, two divide by 2 counters, and a divide by 14 counter. Theoutputs of these counter stages are denoted Tl, T2, T3 T12 and thecomplement outputs are denoted T2, T T17. The outputs are applied togating and decoding circuitry shown in FIGS. 6, l0, l4 and 16.

THE REPRESENTATION OF DATA MARKS AND CHART LINE MARKS AT DIFFERENTINTENSITIES, FIG. 6

The circuitry of FIG. 6 performs most of the functions indicated by thegating and decoding block 34 in FIG. 2 and it produces the compositevideo signal as indicated by the block 38.

In the following description the system will be described as producing a100-line chart such as that of FIG. 4. The switch S1 can be moved to theupper posi tion to produce a SO-line chart.

The composite video and synchronizing signal is developed across theresistor R6. It is produced by switching on or off the appropriatecombination of gates M406-6, M204-6, M108-6, M208-6 and M108-8. Thisvaries the current in resistor R6 and the voltage at the composite videoand sync terminal.

A. Production of the Synchronizing Level.

The television monitor used in this implementation requires thesynchronizing level to the most negative excursion of the compositeinput signal. Synchonizing signals, derived by logical decoding of thestates of counter outputs T9, T10, T11 by gate M401 for horizontalsynchronization and of counter outputs T16, T17, T18, T19, T and T21 bygate M504 for vertical synchronization, eause gate output M406-6 to below. Moreover, the CHART BLANK and DATA BLANK signals are always lowduring synchronizing causing gate outputs M2046, M108-6, M208-6 andM108-8 to also be low. Thus the composite video signal is low, oreffectively ground.

B. Production of the Black Level.

When no synchronizing signal is present, gate output M406-6 is high. Ifthe monitor screen is not to be brightened, as determined by the absenceof chart line, shading line, or data signals, or the absence of theappropriate inverted blanking signal, m or m, gate outputs M204-6,M108-6, M208- 6 and M108-8 are all low. The high state of gate outputM406-6 causes a current flow in R6 sufficient to produce a voltage dropof about 0.3 volts.

C. Production of the Dimmest Visible Level.

At the time when the monitor screen is to be brightened to any level (inorder to display the chart, the time line, the data mark or the shading)gate M204-6 is made high in response to a low value of any of thesignals F, I, C or D. In particular, signal F is low whenever thedecoding of counter outputs T1, T4 and TS indicates that the dimmestfine chart lines are to be displayed. When M204-6 is made high a currentflows in R6 sufficient to produce an additional voltage drop of about0.15 volts. Since the synchronizing pulses are always absent at thesetimes, the latter voltage drop is added to the former one of 0.3 volts,giving a drop in R6 of 0.45 volts when the screen is to be brightened tothe lowest brightness level.

D. Production of Higher Intensity Levels.

Likewise, when the screen is to be brightened to emphasize each fifth ortenth line of the chart, or to cause a time line to be drawn across thedisplay, or to produce a data mark, gate M108 output 6 is made high inresponse to the absence of any of signals I, C or D. In particular,signal I is low whenever the decoding of counter outputs T1, T4, T5 andT6 indicates that each fifth of the chart lines should be displayed, orwhenever the signal TIME LINE is low, indicating, that the data shouldbe accompanied by a time line. When M108 output 6 is high an additionalcurrent flows in R6 to produce, when added to the other currents fromM406 output 6 and M204 output 6, a drop of about 0.6 volts.

When the screen is'to be brightened to emphasize each tenth chart line,decoding of counter outputs T1, T4, T5 and T8 causes input C of gateM208-6 to go low and thus the total voltage drop in R6 is brought to0.75 volts.

The system is capable of displaying three separate data marks on eachraster line. When one of these marks is to be displayed at the brightestlevel in the picture, signal 5 is low, making gate M208-6 high, and oneof the inputs 9 of gate M108-8 is made low, making the output high andbringing the total voltage drop in R6 to about 0.9 volts. These actionsresult from the decoding of all the states of one of the data counters,such as C1, C2, C3, C4, C5, C6, C7, C8, C9 and C10 in FIG. 8, providedthat the switch DISPLAY C is turned ON as shown. The ability to turn theindividual data marks on or off by switches DISPLAY A, DISPLAY B andDISPLAY C aids the operator to identify and interpret the traces.

THE UPDATING CIRCUITRY, INCLUDING SYSTEM CONTROL 45, FIGS. 7-11 FIG. 7is a detail of the shift register 39 of FIG. 2. Stages 2-10 have beendeleted and stages 12-20 have been deleted. The deleted stages are inall ways similar to stages 22-30 which have been shown.

FIG. 8 shows the gates, data counters and decoders 41 of FIG. 2. ThreeIO-stage data counters are provided, one for each of the measuredvariables to be displayed. Only the data counter including the stagesN703-N707 has been entirely shown. These stages make up data counter C.The J-K flip-flop stage M406 is the first stage of data counter B andthe flip-flop N-301 is the first stage of data counter A.

FIG. 9A shows the update flip-flop made up of the logic unit M-706 andFIG. 9B shows the logic circuits M604 and 605 which control the delayline interlace. FIG. 10 shows the shift register control circuit.

FIG. 11 shows the delay line shift flip-flop.

The data record displayed consists of 513 -bit binary words storedserially in the acoustic delay line serial memory (FIG. 2). Analternative implementation of the system would use a set of longsemiconductor shift registers connected serially to have a capacity of465 or more 31-bit words, with appropriate conventional clock, shiftcontrol and refreshing circuits. A third implementation, to perform thesame functions as the other two, would organize the shift registers intothree parallel memory systems, each being a serial memory with acapacity of 465 or more words, two of the systems using 10-bit words andone using ll-bit words. Alternatively, a random access memory with acyclic address system, or a magnetic drum or disc memory can be used.

For convenience and economy the delay line memory has a delay time of 8%milliseconds, and is operated in the conventional interlaced mode sothat each bit is circulated twice through the memory. Every alternatebit is decoded to be used for control purposes at the output.Recirculation to obtain proper interlace is controlled by gates MS-3,M605-6, M604-6 and M604-8, of FIG. 9B. For simplicity, the followingdescription will treat the delay line and its input gating and controlas if it had a delay time of 16 milliseconds and no interlacing.

Only the 465 words which appear at the output of the delay line duringthe scanning of the 465 visible lines of the television monitor screenare used to control the display. Also, only 31 of the 35 bits in eachword are used for control.

At all times during operation of the display the delay line data outputis applied to inputs 2 and 3 of the 32- bit long shift register composedof J-K flip-flops N201 through N208 inclusive, N601, N502 through N507inelusive, and N608 of FIG. 7. This shift register is also provided with31 input gates connected to the wires marked ELI-B31 inclusive, throughwhich parallel data are entered from the external data source, acomputer or other digital device. The states of all stages of theregister are available and used to access the data from the delay linefor control of the monitor picture.

During normal operation of the display the delay line data output isalso applied through gates M605-3, M605-6, M604-6, and M604-8 of FIG. 93to the delay line data input for recirculation without modification. Inthis mode, as each word appears at the delay line data output, it isclocked into the shift register at the same time it is being fed to thedelay line data input through the interlace gates of FIG. 9B. When theshift register is filled, toward the end of a monitor raster line sweepperiod, pulse H1264 is generated by the decoding of counter states T3,T5, T6, T7, T9, T11 and T12 in gates M205-6, M-304-6, M305-6 and M305-8of FIG. 16 and is applied to gates N303, N305, N604, N605 and N606 ofFIG. 8 to set the data counter stages (for example, N301, N406,N703-N707 and N607-9 of FIG. 4) to states complementary to those of thecorresponding stages of the shift register.

When update is called for, data input line BL32 (FIG. 9A) is made high.Then through the action of gates M707-8, M707-11, and M706-8, FIG. 9,when STROBE A is generated by gate N704-6 (FIG. 17) during the rasterline time just preceding the top displayed line of a monitor frame, theupdate flip-flop, M706-3 and M706-6, is set. Near the end of the 464thraster line of the next frame, gates M605-8 and M608-8 (FIG. 15) dropthe CLEAR DATA S.R. signal briefly to ground about nanoseconds after theH1264 pulse has caused transfer of data from the shift register to thedata counters as described above. This resets all stages of the shiftregister to zero. Early in the sweeping of the 465th line of the frame,gate M606-8 (FIG. 15) generates pulse STROBE B to set the states of thefirst 31 shift register stages equal to the states of data input linesBLl-BL31 (which, of course, represent the new updated data). This occursbefore any bit of the next data word appears at the ,D.L. data output.STROBE B also sets the D.L. shift flip-flop, M603-3 and M603- 6.(FIG.11) The resulting change of state of signals S and S changes the signalpaths through gates M60S-6, M604-6 and M604-8 (FIG. 98) so that the DATAS.R. OUTPUT of the shift register is connected to the DELAY LINE DATAINPUT and the DELAY LINE DATA OUTPUT is correspondingly disconnectedfrom DELAY LINE DATA INPUT. As a consequence, the new data word isshifted from the shift register'into the delay line data input while'theformer first data word (to control the data formerly displayed on thetop line of the monitor picture) is shifted from the delay line dataoutput to the shift register during the scanning of the bottom displayedline of the monitor picture. Thereafter the data shift register clockpulses are interrupted by gate M408-3 and flip-flop M407-9 (FIG. 10)until the scanning of the top display line of the next monitor frame.

The foregoing is equivalent to throwing the switch 44 (FIG. 2) to theupper position. This inserts the word from the shift register into thedelay line loop.

During scanning of the 465th line of the frame being discussed, gateM706-ll (FIG. 9A) acts to reset the update flip-flop. If another updateis not required immediately, data input line BL32 will have been resetby the data source to ground level 'before the next STROBE A pulse time.

While the next frame is scanned, during each line scan time the datafrom the shift register output will be shifted into the delay line datainput as data are accepted into the shift register input from the delayline data output, until, late in raster line 464, the delay line shiftflip-flop M-603-3 and M603-6 (FIG. 11) is reset by gate M-603-8. Thischanges signals S and S to their normal states and the signal pathsthrough gates M605- 6, M604-6 and M604-8 (FIG.9B) again connect thedelay line data output directly to the delay line data input. Theforegoing is equivalent to throwing the switch 44 (FIG. 2) back to thelower position while the old 465" word is still in the shift register.Therefore the old 465 word is deleted.

The result of this operation is that the new data word has been put inthe data stream circulating in the delay line in place of the word whichformerly controlled the data presentation for the top line of thedisplay, the data word which controlled the top line has been put inplace of that which controlled the second line, and every other word hasbeen shifted back one line time except the last word, which has beeneliminated from the circulating stream.

THE CIRCUITRY FOR APPLYING THE HORIZONTAL TIME LINES If a time line isrequired to accompany the representation of a given set of data points,line BL31, FIG. 7, from the external data source is made high when theassociated data word is entered by the updating process just described.At the time of updating, when signal STROBE B is high, this causes theshift register stage N608-5 (FIG. 7) to be set, and thus the 31st bit ofthe data word entered in the delay line to be a one.

Whenever a data word has been completely shifted from the delay linedata output into the shift register, shift register stage N608-5 will beset if the 31st bit of the data word is a one, indicating that a timeline accompanies the data. Signal H1264 is briefly made high, openinggate N606-8 (FIG. 8) to set flip-flop N607-9, making signal TIME LINElow, to remain in this state until the next occurrence of HSYNCH towardsthe end of the next raster line. Signal TIME LINE is connected throughgate M306-8, FIG. 6, to make I low, turning on gates M204-6 and M108-6and producing a drop of at least 0.6 volt in R6 during the duration ofthe chart generation period, as defined by the presence of signal CHARTBLANK.

THE CIRCUITRY FOR OBTAINING SHADING Shading, as implemented in thedisplay system described here, extends from the left-hand chart line tothe position of the data mark representing a selected one of the threedisplayed variables. The operator may turn on one of three switches toobtain shading of the variable he has chosen. The three switches are S5,S6 and S7 of FIG. 12. When one of these switches is turned ON, one ofthe three inputs of gate N805-12 is low, enabling gate N803-l1 to passpulse H1397, which is substantially coincident in time with thegeneration of the video signal to produce the left-hand chart line. Thusthe flip-flop made up of gates N806-6 and N806- 11 is set, making theSHADING signal low, and through gates M306-6 and M306-1l(FIG.6) causingsignal F to be low and gate output M204-6 to be high. This gives avoltage drop in R6 of 0.45 volts, causing the monitor screen to bebrightened to the same level as is used to mark the fine chart lines.

The bits of the data word which designate the value of the variableselected by the switch will, prior to the occurrence of pulse H1397,have been used to set one of the three DATA COUNTERS of FIG. 8 to theones complement of the data value. Beginning at the time the leftl ia ri d ghart line signal is generated, the DATA CNTR CLOCK pulses incrementeach of the three tenbit counters. When all the stages of a counterreach the one" state, the corresponding signal, DATA A, DATA B, or DATAC (FIG. 6) goes high. This signal is passed by one of the gates N804-3,N804-6, or N804- 8 (FIG. 12) to reset the flip-flop N806-6 and N806-11,causing the SHADING signal and signal F (FIG. 6) to go high, ending theshading.

OTHER CIRCUITS FIG. 13 shows the circuitry for producing the verticalflyback. Horizontal sync pulses are counted in a divideby-5l3 countermade up of the modules M403, M404 and M405. After counting 513 H SYNCpulses the outputs TT5, T16, T17, TE are applied to the gate N504- 8,FIG. 6, to produce the vertical sync signal. FIG. 14 shows the logiccircuitry for producing the horizontal and vertical blanking pulses andother necessary sig nals, including pulsesat lines 465 and 5l3.

FIG. 15 shows the logic circuitry for producing the CLEAR DATA SHIFTREGISTER and the STROBE B pulses. FIG. 16 shows the logic circuitry forproducing pulses H1264, H1268 and H1270 which occur during each scanline at counts of 1264, 1268 and 1270 respectively. FIG. 17 shows thelogic for producing pulse signals U-L465, (L513'H1270) and STROBE A.FIG. 18 shows gates connected to supply logical one states as requiredin the system.

The following list of typical circuit elements is exemplary and is notto be considered limiting of the invention. In the following tabulation,the designations M101, N102, etc., are the same as those used in FIGS.5-18 and also show the locations which these modules occupy in theactual execution of the invention.

M101 Motorola MC3062 Dual .I-K flip-flop M102 MC3002 Quad 2-input NORgate M103 MC3015 S-input NAND gate M104 MC3010 Dual 4-input NAND gateM105 MC3026 Expandable Dual 2-wide Z-input AND-OR-INVERT gate M106MC3002 Quad 2-input NOR gate M107 MC3000 Quad 2-input NAND gate M108MC3005 Triple 3-input NAND gate M201 Motorola MC3061 Dual .l-K flip-flopM202 MC3062 M203 MC3061 M204 MC3010 Dual 4-input NAND gate M205 MC3006Triple 3-input AND gate M207 MC3061 M208 MC3000 Quad Z-input NAND gateM301 Motorola MC3020 Expandable Dual 2-wide Z-input AND-OR-INVERT gateM303 MC3061 M304 MC3006 Triple 3-input AND gate M305 MC3026 Dual 4-inputAND power gate M306 MC3000 Quad Z-input NAND gate M307 MC3000 QuadZ-input NAND gate M308 MC3005 Tn'ple 3-input NAND gate M401 MotorolaMC3025 Dual 4-input NAND power gate M404 MC839 Divide by 16 counter M405MC839 M406 Instruments SN-7486 Quad Z-input exclusive-OR gate

1. The method of graphically displaying a time variant, digitallysampled, measured variable in moving strip chart format on a cathode raytube system having an intensity modulated electron beam which traversesthe face of the tube along successive scan lines in a raster framecomprising: a. modulating the intensity of said electron beam at aposition in a first scan line of a first raster frame, said positionrepresenting the magnitude of said measured variable at a first time, b.modulating the intensity of said electron beam at positions insuccessive scan lines of said first raster frame, said positionsrepresenting the magnitudes of said measured variable sequentially attimes one preceding another, to produce a trend line along said stripchart format representing said measured variable, c. modulating theintensity of said electron beam at a position in said first scan line ofa later raster frame, said position representing the magnitude of saidmeasured variable at a second time, d. modulating the intensity of saidelectron beam at positions in successive scan lines of said later rasterframe, said positions representing the magnitude of said measuredvariable at times prior to said later time, and e. repeating theforegoing modulating steps for some subsequent raster frames to producesaid moving strip chart format.
 2. The method recited in claim 1 whereina plurality of measured variables are displayed in moving strip chartformat on said cathode ray tube system by modulating the intensity ofsaid electron beam in each scan line at a plurality of positions eachrepresenting the magnitude of one of said measured variables at a giventime.
 3. The method recited in claim 1 further comprising: modulatingthe intensity of said electron beam at the same scale line positions oneach scan line to produce scale lines along said strip chart format,said electron beam being modulated at said scale line positions to adifferent intensity than the modulation at positions representing saidmeasured variable so that the scale lines are readily dinstinguishablefrom said trend line.
 4. The method recited in claim 1 furthercomprising: modulating the intensity of said electron beam in scan linesassociated with particular samples to produce time lines across saidstrip chart format, said time lines being distinguished from said trendline by a different intensity of modulation of said electron beam. 5.The method recited in claim 1 further comprising: modulating theintensity of said electron beam in each scan line between a referenceposition and the position representing the magnitude of said measuredvariable to produce a display which is brightened between a referenceline and said trend line.
 6. The method of graphically displaying amoving strip chart format on a cathode ray tube system having anelectron beam which traverses the face of the tube along successive scanlines, saId strip chart format representing successive values of anindependent variable, and a plurality of stored, digitally encoded datasignals representing measurements of a dependent variable, comprising: afirst step of receiving data signals corresponding to the independentvariable, a second step of storing said data signals, a third step ofcounting clock pulses beginning at the time when the electron beam is ata reference position, a fourth step of producing for each scan line afirst output signal when said clock pulse count corresponds to said datasignal for that scan line, a fifth step of modulating said electron beamto a first intensity as the electron beam is scanned from said referenceposition to a position corresponding to said output signal, a sixth stepof modulating said electron beam to a second intensity at the occurrenceof each of said first output signals, repeating the foregoing steps forthe remaining raster scan lines, and repeating said third through sixthsteps for a later raster frame, the intensity of said electron beambeing modulated in the scan lines of said later raster frame atpositions corresponding to the output signal at times later than thetimes of the output signal for the preceding raster frame, theoccurrence times of said output signal being displaced with respect tothe scan line on which it is displayed on said later raster frame, oneextreme value of said output signal being deleted and one value beingadded at the other extreme.
 7. The method recited in claim 6 whereinsaid system includes a color reproducing cathode ray tube and whereineach of said different intensities is represented by a different coloron the face of said cathode ray tube.
 8. The method recited in claim 6further comprising: a seventh step of producing a plurality of secondoutput signals at predetermined clock count intervals, and an eighthstep of modulating the electron beam to a preselected intensity at theoccurrence of each of said second output signals to produce verticalscale lines along said strip chart format.
 9. The method recited inclaim 8 further comprising: a ninth step of producing a third outputsignal at preselected intervals of said independent variable, a tenthstep of storing said signal produced in the ninth step in propersequence with said data for said dependent variable, and an eleventhstep of modulating the electron beam to another preselected intensity toproduce horizontal time lines on said strip chart format.
 10. A graphiccathode ray tube display system for displaying stored digital data of aplurality of measured variables, said system having a raster scan linetype electron beam positioning circuit and intensity modulating controlcircuit comprising: a source of clock pulses dividing said scan lineinto equal time increments, counter means for receiving said clockpulses including means for resetting said counter once during each scanline, a digital data storage device for storing data for each of saidmeasured variables, the number of data for each variable correspondingto the number of displayed scan lines of said cathode ray tube display,means for selecting from storage a particular digital data prior to thebeginning of each scan line, means for producing from said counter afirst output when said counter reaches a count corresponding to saidparticular digital data, means responsive to said first output tomodulate the intensity of the electron beam during each scan linethereby producing a trend line representing said measured variable, andmeans for updating said data storage device after the scanning of all ofsaid scan lines, said data being displaced with respect to the scan lineon which it is displayed on a subsequent scanning of said scan lines,one extreme data value being deleted and one data value being added atthe other extreme.
 11. The system recited in claim 10 furthercomprising: means for producing from said counter a second output atpredetermined count intervals for scaling each scan line, and meansresponsive to said second output for modulating the intensity of saidelectron beam at a different intensity level to produce scale linesreadily distinguishable from said trend line.
 12. The system recited inclaim 10 further comprising: means for producing a third output duringscanning of scan lines corresponding to particular data, and meansresponsive to said third output for modulating the intensity of saidelectron beam at a different intensity level to produce time linesreadily distinguishable from said trend lines.
 13. The system recited inclaim 10 further comprising: means for producing from said counter afourth output at the occurrence of a preselected reference count, abistable device being set to one of its states upon the earlieroccurrence of said first or fourth outputs and reset to the other of itsstates upon the later occurrence of said first or fourth outputsrespectively, and means responsive to the output of said bistable deviceto modulate said electron beam with a different intensity between saidreference count and said count corresponding to said particular digitaldata.
 14. A graphic cathode ray tube display system for displayingstored digital data of a plurality of measured variables, said systemhaving a raster scan line type electron beam positioning circuit andintensity modulating control circuit comprising: a source of clockpulses dividing said scan line into equal time increments, a firstcounter for receiving said clock pulses including means for resettingsaid counter once during each scan line, a digital data storage devicefor storing data for each of said measured variables, the number of datafor each variable corresponding to the number of displayed scan lines ofsaid cathode ray tube display, means for selecting from storage aparticular digital data prior to the beginning of each scan line, asecond counter for producing a first output when said second counterreaches a count corresponding to said particular digital data, meansresponsive to said first output to modulate the intensity of theelectron beam during each scan line thereby producing a trend linerepresenting said measured variable, and means for updating said datastorage device after the scanning of all of said scan lines, said databeing displaced with respect to the scan line on which it is displayedon a subsequent scanning of said scan lines, one extreme data valuebeing deleted and one data value being added at the other extreme. 15.The system recited in claim 14 further comprising: means for producingfrom said first counter a second output at predetermined count intervalsfor scaling each scan line, and means responsive to said second outputfor modulating the intensity of said electron beam at a differentintensity level to produce scale lines readily distinguishable from saidtrend line.
 16. The system recited in claim 14 further comprising: meansfor producing a third output during scanning of scan lines correspondingto particular data, and means responsive to said third output formodulating the intensity of said electron beam at a different intensitylevel to produce time lines readily distinguishable from said trendlines.
 17. The system recited in claim 14 further comprising: means forproducing from said first counter a fourth output at the occurrence of apreselected reference count, a bistable device being set to one of itsstates upon the earlier occurrence of said first or fourth outputs andreset to the other of its states upon the later occurrence of said firstor fourth outputs respectively, and means responsive to the output ofsaid bistable device to modulate said electron beam with a differentintensity between said reference count and said count corresponding tosaid particular digital data.